This invention relates to terminal connection of electrical conductors and particularly directed to clamping devices which hold electrical conductors such as in pilot devices or the like.
In the past, numerous devices have been proposed for securing electrical conductors in a terminal block. Clearly the most pertinent is U.S. Pat. No. 3,246,283, issued Apr. 12, 1966 to Paul Huska, the inventor in the present case. However, the +283 patent discloses a device wherein securing of the electrical conductor (or conductors) within the terminal block is dependent upon the craftsman turning a screw to open the terminal block to receive the conductor and, subsequently, reversing the screw to clamp the conductor end, while holding the conductor end in the desired position within the terminal block. The above is an over simplification of the work to be performed.
Terminal blocks are usually used to secure electrical or electronic conductors in communication systems, instrumentation systems and control systems from the simple to the most complex. It is obvious, therefore, that the highest degree of reliability be secured for conductor terminations. The integrity of any system is greatly contingent upon workmanship and adequacy of the terminal blocks.
Furthermore, mechanical motion, vibration, temperature variations, cold flow characteristics of materials used, realignment of conductor strands, especially where more than one conductor occupies the same "clamp space" affect proper connection. Under such conditions the reliability of the electrical/electronic systems noted above is of great concern. Indeed, life, property and equipment may be in jeopardy.
Moreover circuitry could be adversely affected due to changes in resistance values of a given circuit. Especially critical, is the problem of a conductor withdrawing from a terminal block because of the loosening actions described above. This occurs in many instances where conductors are installed under tension. Hence, when the force is great enough, a conductor will pull out and away from its terminal block. These kinds of occurrences, and they are frequent, can be disastrous. The present invention overcomes these problems and provides improved means for attaching the terminal block to a mounting rail.
A search in the U.S. Patent Office has revealed various other patents which are generally related to the present invention. The most pertinent patents found in the search are the following:
______________________________________ Patent No. Inventor Issue Date ______________________________________ 1,439,657 R. Zollner Dec. 19, 1922 1,642,042 J. L. Polk Sept. 13, 1927 2,166,346 H. A. Douglas July 18, 1939 3,001,173 A. H. Swengel Sept. 19, 1961 3,152,855 E. C. Crowther Oct. 13, 1964 3,304,392 E. W. Isler Feb. 14, 1967 3,915,545 Y. Saito Oct. 28, 1975 3,989,345 C. P. DeVito Nov. 2, 1976 4,476,400 T. Jo et al Oct. 9, 1984 4,643,513 C. B. Martin Feb. 17, 1987 ______________________________________
The Isler, Saito, Swengel, Martin and Zollner patents each suggests the use of spring clamping means. However, none of these provides a quickly releasable means for locking the clamping means in a fully open position to facilitate insertion of a conductor therein. The patents of Polk, Douglas, Crowther, DeVito and Jo are generally related to the subject matter of the present invention, but are believed to be less pertinent than those patents referred to above.
Over the course of prosecution of the parent application, several patents having screw means were cited as pertinent by the Examiner as follows:
______________________________________ Patent No. Inventor Issue Date ______________________________________ 2,011,861 H. Knumann Aug. 1935 3,246,283 P. Huska April 12, 1966 3,304,392 E. W. Isler Feb. 14, 1967 4,004,846 H. Woertz Jan. 25, 1977 ______________________________________
Each of these patents disclose a screw means for actuating or releasing an electrical connection. However, none of the patents disclose a screw means with the unique configuration of the invention which allows quick release and quick securement with a minimum of screw means rotation.
Another search of the U.S. Patent Office specifically directed to the screw of the invention disclosed the following U.S. Patents:
______________________________________ Patent No. Inventor Issue Date ______________________________________ 389,028 J. P. Wallace Sept. 4, 1888 452,640 P. A. Gerry May 19, 1891 1,052,179 C. J. Robley Feb. 4, 1913 1,987,474 A. E. Grant Jan. 8, 1935 2,445,396 H. D. Gursky July 20, 1948 2,929,474 S. Boardman Mar. 22, 1960 4,235,560 V. R. Schimmel Nov. 25, 1980 4,616,818 P. Vischer Oct. 14, 1986 4,734,061 H. E. Randall, Jr. et al May 29, 1988 ______________________________________
A more in-depth description of each of the more pertinent patents follows.
The Schimmel U.S. Pat. No. 4,235,560 patent discloses a transition bolt 12, which is adapted to pass through selected slots 38, inside rails of a reinforcing frame. The transition bolt 13, shown in FIG. 3, is of one-piece character and comprises a flat-sided steel member which may be formed of flat bar stock. The bolt 12 has an enlarged head 52, at one end thereof and an intermediate shoulder portion 54 of intermediate or reduced size, and a further reduced shank portion 56 at its other end. The shoulder and shank portion 52 and 54 are adapted respectively to extend through the horizontal extending slot 33.
The Vischer U.S. Pat. No. 4,616,818 patent is directed to a device for feeding cardboard carton blanks to a conveyer. An adjusting screw means 200 has a relatively small diameter threaded portion 202 and a second relatively large diameter threaded portion 204 for purposes of engaging different surfaces. The head portion of the screw 200 includes a thumb wheel portion 210 which is located adjacent a hexagonal end portion 212. However, a larger second threaded portion 204 is not provided with opposing flat surfaces.
The Grant U.S. Pat. No. 1,987,474 patent is directed to a screw adapted to cut an internal thread within a bore. The screw is provided with a slotted head 11 and a shank portion 10 which is formed with a pair of opposing flat surfaces 12 and connecting rounded surfaces 13 on which ridges 14 are pressed, forming threads on the rounded portion.
The Randall U.S. Pat. No. 4,734,061 patent is directed to a terminal block for use in terminating telecommunications wire. The threaded plug 13 is provided with an extending head 15 on one end of a threaded end insert 33 provided on the opposing end. However, the threaded insert 33 is provided with only a single threaded portion.
The Boardman U.S. Pat. No. 2,929,474 patent is directed to a threaded fastener adapted to provide a means for retaining the fastener in position to prevent loss or displacement during assembly. A bolt 13 is provided with an upper threaded section 15 and a lower threaded end portion 17. The upper threaded portion 15 engages a speed nut 29 for retaining the bolt 13 with a bearing block 23, while the lower threaded portion 17 passes through a base unit 40 to engage a nut 45.
The Gursky U.S. Pat. No. 2,445,396 patent is directed to a clamping device to secure a sheet of sandpaper to a cylinder. A screw member 18 is provided with a differential screw thread arrangement wherein the forward portion 18a is provided with a predetermined thread arranged in one direction, while a larger second portion 18b is provided with an oppositely directly finer thread. Thus, the screw 18 provides a means for engaging different surfaces to provide mechanical clamping therebetween.
The remaining patents found were all directed to other screws having one or more of the elements of the searched invention in common. However, none of them are any more pertinent than those specifically described.
Each of these patents, again fail to disclose the unique aspects of the instant invention which overcomes the problems of laborious turning of a screw means to engage or release a surface of a plate or body.